Leakage resistant RRAM/MIM structure

ABSTRACT

An integrated circuit device includes a resistive random access memory (RRAM) cell or a MIM capacitor cell having a dielectric layer, a top conductive layer, and a bottom conductive layer. The dielectric layer includes a peripheral region adjacent an edge of the dielectric layer and a central region surrounded by the peripheral region. The top conductive layer abuts and is above dielectric layer. The bottom conductive layer abuts and is below the dielectric layer in the central region, but does not abut the dielectric layer the peripheral region of the cell. Abutment can be prevented by either an additional dielectric layer between the bottom conductive layer and the dielectric layer that is exclusively in the peripheral region or by cutting of the bottom electrode layer short of the peripheral region. Damage or contamination at the edge of the dielectric layer does not result in leakage currents.

BACKGROUND

The present disclosure relates to integrated circuit devices withresistive random access memory or metal-insulator-metal capacitors,methods of making such devices, and methods of operating such devices.

Resistive random access memory (RRAM) has a simple structure, lowoperating voltage, high-speed, good endurance, and CMOS processcompatibility. RRAM is a promising alternative to provide a downsizedreplacement for traditional flash memory and is finding wide applicationin devices such as optical disks and non-volatile memory arrays.

An RRAM cell stores data within a layer of material that can be inducedto undergo a phase change. The phase change can be induced within all orpart of the layer to switch between a high resistance state and a lowresistance state. The resistance state can be queried and interpreted asrepresenting either a “0” or a “1”.

In a typical RRAM cell, the data storage layer includes an amorphousmetal oxide. Upon application of a sufficient voltage, a metallic bridgeis induced to form across the data storage layer, which results in thelow resistance state. The metallic bridge can be disrupted and the highresistance state restored by applying a short high current density pulsethat melts or otherwise breaks down all or part of the metallicstructure. The data storage layer quickly cools and remains in the highresistance state until the low resistance state is induced again. RRAMcells are typically formed after front-end-of line (FEOL) processing. Ina typical design, an array of RRAM cells is formed between a pair ofmetal interconnect layers.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is an illustration of an integrated circuit device providing anexample in accordance with a first group of embodiments provided by thepresent disclosure.

FIG. 2 is an expanded view of a portion of FIG. 1.

FIG. 3 is an illustration of an integrated circuit device providing anexample in accordance with a second group of embodiments provided by thepresent disclosure.

FIG. 4 is an expanded view of a portion of FIG. 3.

FIG. 5 is a flow chart of a method, which is an example in accordancewith some embodiments of the present disclosure.

FIGS. 6 and 7A illustrate a device, which can be the device of FIG. 1 orthe device of FIG. 3, as it begins manufacture according to the processof FIG. 5.

FIGS. 7B-7C illustrate alternative structures for the bottom electrodeand provide alternative embodiments within either the group ofembodiments represented by the device of FIG. 1 or the group ofembodiments represented by the device of FIG. 3.

FIGS. 8 to 11 illustrate the device of FIG. 1 as it undergoes furtherprocessing according to the method of FIG. 5.

FIGS. 12 to 15 illustrate the device of FIG. 3 as it undergoes furtherprocessing according to the method of FIG. 5.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

It has been observed that an RRAM dielectric can be damaged orcontaminated by etching and that this can lead to leakage currentsthrough a peripheral region adjacent an outer edge of the RRAMdielectric layer. The present disclosure provides a method and resultingstructures in which such leakage does not occur. The method modifies thestructure of the RRAM cell stack to cause the separation between the topelectrode and the bottom electrode to be substantially greater about aperipheral region of the top electrode in comparison to a minimumseparation that occurs in a central region. In a first group ofembodiments, the additional separation is created by forming an extralayer of dielectric in the peripheral region. In a second group ofembodiments, the additional separation is created by cutting off thebottom electrode short of the peripheral region. In alternate embodiesthese method and structures are applied to form metal-insulator-metal(MIM) capacitors, which are generally similar in structure to RRAMcells.

FIGS. 1 and 2 illustrate a metal-insulator-metal structure 110A in anintegrated circuit device 100, which is an example within the firstgroup of embodiments provided by the present disclosure. Themetal-insulator-metal structure 110A is typically one cell in an arrayof similar cells. In some embodiments, the metal-insulator-metalstructure 110A is an RRAM cell. In some other embodiments, themetal-insulator-metal structure 110A is an MIM capacitor. The device 100includes a substrate 101 over which is formed a contact 105 within amatrix of dielectric 103. In most embodiments substrate 101 includes oneor more metal interconnect layers formed over a semiconductor body.

Contact 105 can connect to a switching device for selectingmetal-insulator-metal structure 110A. A switching device can be formedon the semiconductor body within substrate 101. In some embodiments theswitching device is a transistor and the structure 110A is one in anarray of RRAM cells having the 1T1R architecture. In some embodiments,the switching device is a diode and the structure 110A is one in anarray of RRAM cells having the 1D1R architecture. In some embodiments,the switching device is a bipolar junction transistor and the structure110A is one in an array of RRAM cells having the 1BJT1R architecture. Insome embodiments, the switching device is a bipolar switch and thestructure 110A is one in an array of RRAM cells having the 1S1Rarchitecture. In some embodiments, there is no switching device and thestructure 110A is one in an array of RRAM cells having the 1Rarchitecture.

An RRAM/MIM (RRAM cell or MIM capacitor) stack 130A is formed over thecontact 105. Contact 105 and dielectric 103 can be part of a metalinterconnect layer formed over the substrate 101. In some embodiments,the structure 110A is an RRAM cell and contact 105 and dielectric 103are part of the fourth (M4) metal interconnect layer. In someembodiments, an etch stop layer 107 is formed over the metalinterconnect layer that includes contact 105. In those embodiments, etchstop layer 107 can include an opening over contact 105 that allowsRRAM/MIM stack 130A to interface with contact 105.

RRAM/MIM stack 130A includes bottom electrode 109, a dielectric layer113, which can be an RRAM dielectric, top electrode 115, and anadditional dielectric layer 111. Bottom electrode 109 can includediffusion barrier layer 109A and main bottom electrode layer 109B. Topelectrode 115 can include capping layer 115A and main top electrodelayer 115B. RRAM/MIM stack 130A includes a central region 124 and aperipheral region 122. Additional dielectric layer 111 extends throughperipheral region 122, but not through central region 124.

Top electrode 115 covers an upper surface of dielectric layer 113.Dielectric layer 113 covers an upper surface of bottom electrode 109. Insome embodiments, top electrode 115 is coextensive with dielectric layer113. In some embodiments, top electrode 115 and bottom electrode 109shadow the same area of substrate 101.

FIG. 2 provides an expanded view of the region 120 identified in FIG. 1.As shown in FIG. 2, the distance 108, which is the shortest distancebetween any point on top electrode 115 within peripheral region 122 andany point on bottom electrode 109, is much greater than the shortestdistance 132 between any point on top electrode 115 within centralregion 122 and bottom electrode 109. In some embodiments, the distance108 is at least about twice the distance 132. In most embodiments,dielectric layer 111 has a lower dielectric constant than the materialof dielectric layer 113. In most embodiments, the resistance along theshortest path 108 from top electrode 115 in peripheral region 122 tobottom electrode 109 is more than twice the resistance along theshortest path 132 from top electrode 115 in central region 124 to bottomelectrode 109.

Dielectric layer 113 may be damaged or contaminated as a result ofetching near an edge 114. Any such damage or contamination is restrictedto an area 112 proximate edge 114 and will not significantly affect theperformance of the device 100. The area 112 is entirely withinperipheral region 122. Because of the greater electrode separation alongpathways through peripheral region 122, leakage will not occur to anysignificant degree through peripheral region 122. In embodiments wherestructure 110A is an RRAM cell, conductive bridges will ordinarily notform through any portion of dielectric layer 113 that is in peripheralregion 122. Conductive bridges will form exclusively within centralregion 124.

FIGS. 3 and 4 illustrate a metal-insulator-metal structure 110B in anintegrated circuit device 200, which is an example within the secondgroup of embodiments provided by the present disclosure. In someembodiments, the metal-insulator-metal structure 110B is an RRAM cell.In some other embodiments, the metal-insulator-metal structure 110B isan MIM capacitor. The description of integrated circuit device 100 andits embodiments applies to integrated circuit device 200 with twodifferences: additional dielectric layer 111 can be absent frommetal-insulator-metal structure 110B and in metal-insulator-metalstructure 110B, bottom electrode 109 is cut off short of peripheralregion 122. As a consequence, in metal-insulator-metal structure 110Bbottom electrode 109 lies exclusively within central region 124 andbottom electrode 109 shadows a smaller area of substrate 101 than topelectrode 115. In most of these embodiments, dielectric 113 covers anedge surface 118 of bottom electrode as shown in FIG. 4.

FIG. 4 provides an expanded view of the region 120B identified in FIG.3. As shown in FIG. 4, shortest distance 108 between top electrode 115in peripheral region 122 and any point on bottom electrode 109 lies in adifferent direction for device 200 as compared to device 100, butdistance 108 is still much greater than the shortest distance 132 withincentral region 122. Accordingly, device 200 achieves the same results asdevice 100.

As shown in FIGS. 2 and 4, in both structure 110A and 110B, the base 136of dielectric layer 113 within central region 124 contacts bottomelectrode 109, but the base 126 of dielectric layer 113 withinperipheral region 122 does not. In embodiments represented by structure110A, this is because additional dielectric layer 111 seperatesdielectric layer 113 from bottom electrode 109 in peripheral region 122.In embodiments represented by structure 110B, this is because bottomelectrode 109 is absent beneath dielectric layer 113 in peripheralregion 122. In both groups of embodiments, a shortest-distance path fromtop electrode 115 to bottom electrode 109 is not found in region 112where dielectric layer 113 may be damaged by etching that forms edge114.

FIG. 5 provides a flow chart of a method 300, which is an exampleaccording to another embodiment of the present disclosure. The method300 can be used to form the device 100 or the device 200. Someembodiments of manufacturing methods are described below with referenceto FIGS. 6-15, which depict incremental manufacturing steps as a seriesof cross-sectional views. More particularly FIGS. 6-11 show onemanufacturing methodology embodiment for manufacturing device 200 whileFIGS. 12-15 show another manufacturing embodiment for manufacturingdevice 100.

In FIG. 6, process 300 begins with optional acts of completingfront-end-of-line (FEOL) processing (FIG. 5, act 301 and act 303) inwhich first (M1) through fourth (M4), contact 105, and dielectric layer103 are formed. An etch stop layer 107 is then formed over the metalinterconnect layer on substrate 101 (FIG. 5, act 305) and a hole 128 isformed through etch stop layer 107 to expose contact 105 as show in FIG.6.

Process 300 continues with a series of acts 310 that form RRAM/MIM stack130 (RRAM/MIM stack 130A or RRAM/MIM stack 130B). An example of how thisRRAM/MIM stack 130A is now described below.

FIGS. 7A-7C shows several different ways to form bottom electrode 109(FIG. 5, act 320), which can include one or more layers. For example, inthe illustrated embodiments of FIGS. 7A-7C, a diffusion barrier layer109A can be formed (FIG. 5, act 321), and a main bottom electrode layer109B is then formed thereover (FIG. 5, act 323). Diffusion barrier layer109A can be included to prevent contamination of main bottom electrodelayer 109B by material from underlying contact 105. In some embodimentscontact 105 is copper and diffusion barrier layer 109A is a material TiNfor example, that provides an effective barrier to copper diffusion. Ingeneral, diffusion barrier layer 109A can have any suitable composition.In most embodiments, diffusion barrier layer 109A is a conductive oxide,nitride, or oxynitride of a metal selected from the group consisting ofAl, Mn, Co, Ti, Ta, W, Ni, Sn, Mg, and combinations thereof. Diffusionbarrier layer 109A can have any suitable thickness. A suitable thicknessis large enough to provide an effective diffusion barrier while notbeing so large as to cause excessive resistance. In most embodiments,the thickness of diffusion barrier layer 109A is in the range from 20 Åto 300 Å. In some embodiments, the thickness of diffusion barrier layer109A is in the range from 100 Å to 300 Å, for example, 200 Å.

Main bottom electrode layer 109B can have any suitable composition.Examples of compositions that can be suitable include, withoutlimitation, metals, metal nitrides, and doped polysilicon. In someembodiments, bottom electrode layer 109B is a metal. The metal can be,for example, Al, Ti, Ta, Au, Pt, W, Ni, Ir, Cu, or a combinationthereof. In some embodiments, bottom electrode layer 109B is a metalnitride. The metal nitride can be, for example, TaN. In someembodiments, bottom electrode layer 109B is a doped polysilicon. A dopedpolysilicon can be either a p+ doped polysilicon or an n+ dopedpolysilicon. In most embodiments, the thickness of bottom electrodelayer 109B is in the range from 20 Å to 200 Å. In some embodiments, thethickness of bottom electrode layer 109B is in the range from 50 Å to150 Å, for example, 100 Å.

The bottom electrode layers 109A and 109B can be formed by any suitableprocesses. In FIG. 7A, for example, bottom electrode layer 109A isdeposited (act 321, FIG. 5) to fill hole (FIG. 6, 128) and is thenchemically mechanically polished down to etch stop layer 107, wherebybottom electrode layer 109A just fills hole 128. Main bottom electrodelayer 109B is then deposited (act 323) to form a structure as shown inFIG. 7A. In FIG. 7B, CMP is not performed on the deposited diffusionbarrier layer 109A (or CMP is performed, but for less time than in FIG.7A), such that some remaining amount of diffusion barrier layer 109A isallowed to cover the surface of etch stop layer 107. In FIG. 7C, thelayers of bottom electrode 109 conform to the surface over which theyare deposited. In this later situation, the shapes of all layers inRRAM/MIM stack 130 are affected by the shape of hole 128 over which theRRAM/MIM stack 130 is formed. Any of the structures as shown in FIGS.7A-7C can be used in conjunction with embodiments exemplified by device100 of FIGS. 1 and 2 or device 200 of FIGS. 3 and 4.

FIGS. 8-11 illustrate intermediate stages of device 200 as one or moreacts 330 that create separation between peripheral top electrode region115 and peripheral bottom electrode region 109. These can include eitheror both of act 331, patterning to remove bottom electrode 109 fromperipheral region 122, and act 333, forming additional dielectric layer111 and patterning to remove a portion of additional dielectric layer111 lying within central region 124. Act 331 results in devices such asdevice 200 illustrated by FIGS. 3-4. FIGS. 8-11 illustrate intermediatestages of device 200 as it undergoes manufacture by the process 300 whenact 331 is employed. FIG. 8 (act 331, FIG. 5, patterning to removebottom electrode 109 from peripheral region 122 and outer region 142),generally includes photolithography to form a mask (not shown) thatcovers central bottom electrode 124 while exposing peripheral bottomelectrode region 122 and outer bottom electrode region 142. With thismask in place, an etch is performed to remove the exposed peripheral andouter bottom electrode regions 122, 142. The mask is then stripped toform a structure as shown in FIG. 8, in which only the central bottomelectrode region 124 remains in place. In most embodiments, the etch caninclude dry and/or wet etching for which etch stop layer 107 provides anetch stop. The dry etch can be, for example, a plasma etch using afluorine-based gas or Ar. The wet etch can be, for example, a wet etchusing HF or a similar acid.

In FIG. 9 an RRAM dielectric layer 113 is formed (act 335, FIG. 5), anda top electrode 115 is formed thereover (acts 340, FIG. 5). Thedielectric layer 113, which can be referred to in some embodiments as afirst dielectric layer, includes a central dielectric region 902 that isin direct contact with at least an upper surface of the bottom electrodelayer 109B. The dielectric layer 113 also includes an outer dielectricregion 904 spaced apart from the bottom electrode layers 109, and aperipheral dielectric region 906 connecting the central and outerdielectric regions. The peripheral dielectric region 906 is spaced apartfrom the bottom electrode layers 109.

In RRAM device embodiments, dielectric 113 can be any material suitablefor the data storage layer of an RRAM cell. A material suitable for thedata storage layer of an RRAM cell is one that can be induced to undergoa reversible phase change between a high resistance state and a lowresistance state. In some embodiments, the phase change is between anamorphous state and a metallic state. The phase change can beaccompanied by or associated with a change in chemical composition. Forexample, an amorphous metal oxide may lose oxygen as it undergoes aphase change to a metallic state. The oxygen may be stored in a portionof dielectric 113 that remains in the amorphous state or in an adjacentlayer, especially capping layer 115A. Although described as adielectric, only the low resistance state need be a dielectric. In mostRRAM embodiments, dielectric 113 is a high-k dielectric while in the lowresistance state. In some RRAM embodiments, dielectric 113 is atransitional metal oxide. Examples of high-k dielectric materials thatcan be suitable for dielectric 113 in RRAM devices include, withoutlimitation, NiO_(x), Ta_(y)O_(x), TiO_(x), HfO_(x), Ta_(y)O_(x), WO_(x),ZrO_(x), Al_(y)O_(x), SrTiO_(x) and combinations thereof. In most RRAMembodiments, the thickness of dielectric 113 is in the range from 20 Åto 100 Å. In some RRAM embodiments, the thickness of dielectric 113 isin the range from 30 Å to 70 Å, for example, 50 Å.

In MIM capacitor embodiments, dielectric 113 can be any materialsuitable for the insulating layer of an MIM capacitor. In some MIMcapacitor embodiments, dielectric layer 113 is silicon oxynitride orsilicon nitride. In most MIM capacitor embodiments, dielectric layer 113is a high-k dielectric. In some MIM capacitor embodiments, dielectriclayer 113 is a hafnium compound. Examples of hafnium compounds includehafnium oxide (HfOZ), hafnium silicon oxide (HfSiO), hafnium siliconoxynitride, (HfSiON), hafnium tantalum oxide (HfTaO), hafnium titaniumoxide (HfTiO), hafnium Zirconium oxide (HfZrO), and combinationsthereof. Dielectric layer 113 can include multiple layers of variousdielectrics. In most MIM capacitor embodiments, the thickness ofdielectric 113 is in the range from 50 Å to 300 Å. In some MIM capacitorembodiments, especially those in which dielectric 113 is a high-kdielectric, the thickness of dielectric 113 is in the range from 50 Å to100 Å.

When dielectric layer 113 is formed over a bottom electrode 109 shapedas illustrated for the device 100C shown in FIG. 7C, it is possible thata deposition process will result in dielectric layer 113 being slightlythicker in peripheral region 222 as compared to a minimum thickness ofdielectric layer 113 occurring in central region 224. A slightly greaterseparation between bottom electrode 109 and top electrode 115 inperipheral region 222 resulting solely from that thickness variationwould not be considered substantial as that term is used in the presentdisclosure. By contrast, the difference in separation resulting fromeither act 331 or act 333 would be considered substantial.

As shown in FIG. 9, top electrode 115 when initially formed includes acentral top electrode region 908, a peripheral top electrode region 910,and an outer top electrode region 912 Top electrode 115 can include oneor more layers. Top electrode 115 includes a main top electrode layer115B of conductive material. In some embodiments, especially the RRAMembodiments, top electrode 115 also includes capping layer 115A. ForRRAM embodiments, capping layer 115A can provide an oxygen storagefunction that facilitates the setting and resetting of the RRAM cellformed by metal-insulator-metal structure 110.

Capping layer 115A can have any suitable composition. In some RRAMembodiments, capping layer 115A is a metal or a metal oxide that isrelatively low in oxygen concentration. Examples of metals that can besuitable for capping layer 115A in RRAM embodiments include Ti, Hf, Pt,Al or a combination thereof. Examples of metal oxides that can besuitable for capping layer 115A include TiO_(x), HfO_(x), ZrO_(x),GeO_(x), CeO_(x), or a combination thereof. Capping layer 115A can haveany suitable thickness. In most RRAM embodiments, the thickness ofcapping layer 115A is in the range from 20 Å to 100 Å. In some RRAMembodiments, the thickness of capping layer 115A is in the range from 30Å to 70 Å, for example, 50 Å.

Main top electrode layer 115B can have any of the compositionsidentified as suitable for main bottom electrode layer 109B. Topelectrode layer 115B can have any suitable thickness. In mostembodiments, the thickness of top electrode layer 115B is in the rangefrom 100 Å to 400 Å. In some embodiments, the thickness of top electrodelayer 115B is in the range from 150 Å to 300 Å, for example 250 Å.

In FIG. 10, the RRAM/MIM stack is patterned to formmetal-insulator-metal structure 110A (act 351, FIG. 5). To form thestructure of FIG. 10, photolithography is typically used to form a mask(not shown) over the top electrode layer 115B. This mask exposes outertop electrode regions 912, while covering the central and peripheral topelectrode regions 908, 910. With the mask in place, an etch process (Act351, FIG. 5) etches through at least top electrode layers 115 anddielectric layer 113 and removes the outer top electrode regions 912 andouter dielectric regions 904, while leaving the central and peripheraltop electrode and dielectric regions (902, 906, 908, 910) in place. Inmost embodiments, the etch is a plasma etch for which etch stop layer107 provides an etch stop. The etch can be carried out in one or morestages to etch through the various layer of RRAM/MIM stack 130. Theindividual stages can be, for example, plasma etches based on one ormore of Cl₂, BCl₂, Ar, and F. In most embodiments, act 351 uses a singlemask.

As shown in FIG. 10, for example, act 351 forms edge 116 of topelectrode 115 and edge 114 of dielectric layer 113. In most embodiments,act 351 leaves edge 116 and edge 114 flush as shown in FIGS. 2 and 4.Edges 114 and 116 are at the periphery of metal-insulator-metalstructure 110, abut peripheral region 122, and are distal to centralregion 124. Capping layer 115A may be damaged or contaminated near edge116. Dielectric layer 113 may be damaged or contaminated near edge 114.Any such damage or contamination does not affect the performance ofmetal-insulator-metal structure 110 provided by the present disclosure.In some embodiments, act 351 includes etching through bottom electrode109 and leaves an edge 106 of bottom electrode 109 also flush with edge114 of dielectric 113 as shown in FIG. 14.

Process 300 continues with acts that encapsulate metal-insulator-metalstructures 110 in dielectric 119 and form a top electrode via 125 forconnecting metal-insulator-metal structures 110 to bit lines (not shown)or the like. Act 353 deposits dielectric 119. Act 355 forms an opening134 in dielectric 119 as shown in FIG. 11 for device 200 and FIG. 15 fordevice 100. Act 357 fills opening 134 with conductive material to formvia 125 resulting in a structure as shown in FIG. 1 for device 100 andFIG. 3 for device 200. In most embodiments, dielectric 119 is a low-kdielectric. In some embodiments, dielectric 119 is an extremely low-kdielectric. Via 125 can be formed from any suitable conductor. In someembodiments, via 125 is copper.

FIGS. 12-15 illustrate an alternate manufacturing embodiment to formdevices such as device 100 illustrated in FIGS. 1-2. Many acts inmanufacturing device 100 are the same as described above with regards tomanufacturing device 200, and are therefore not repeated for purposes ofclarity and conciseness. Act 333 of FIG. 5 is present, however, and wasnot previously described in FIGS. 6-11. FIGS. 12-15 illustrateintermediate stages of device 100 as it undergoes manufacture by theprocess 300 when act 333 is employed.

In FIG. 12 (Act 333, forming additional dielectric layer 111), generallyincludes photolithography to form a mask (not shown) that exposes acentral region of additional dielectric layer 111, while coveringperipheral and outer regions of the additional dielectric layer 111. Anetch is carried out with the mask in place to remove the exposed centralportion of additional dielectric layer 111, and the mask is thenstripped to form a structure as shown in FIG. 12. As shown in FIG. 12,act 333 leaves peripheral dielectric region 122 and outer dielectricregion 142. Additional dielectric layer 111 can have any suitablecomposition and can be formed by any suitable process. Examples ofsuitable compositions for additional dielectric layer 111 include,without limitation, SiO₂, SiN, and SiON.

Additional dielectric layer 111 can have any suitable thickness.Additional dielectric layer 111 is sufficiently thick to perform itsfunction but is generally not so thick as to excessively increase theheight of RRAM/MIM stack 130A. In most embodiments, the thickness ofadditional dielectric layer 111 is in the range from 10 Å to 200 Å. Insome embodiments, the thickness of additional dielectric layer 111 is inthe range from 20 Å to 100 Å, for example, 50 Å. As shown in FIGS.13-14, a MIM/RRAM dielectric 113 and top electrode layers 115 are thenconformally formed over the dielectric layer. Etching is then performedto remove outer regions of the layers while leaving peripheral andcentral regions in place, as shown in FIG. 14.

The present disclosure provides an integrated circuit device thatincludes a metal-insulator-metal structure. The structure can form aresistive random access memory (RRAM) cell or an MIM capacitor. Themetal-insulator-metal structure includes a dielectric layer between atop conductive layer and a bottom conductive layer. The dielectric layerincludes a peripheral region adjacent an edge of the dielectric layerwhere the dielectric layer has been cut off by etching and a centralregion surrounded by the peripheral region. The top conductive layerabuts and is above dielectric layer. The bottom conductive layer abutsand is below the dielectric layer in the central region. The bottomconductive layer does not abut the dielectric layer in the peripheralregion of the dielectric layer.

This structure causes pathways between the top conductive layer and thebottom conductive layer to be substantially greater along pathwayspassing through the peripheral region of the dielectric layer incomparison to pathways passing through the central region. This inhibitsformation of conductive bridges or leakage currents through areas of thedielectric layer that may have been damaged or contaminated by etchingnear the edge of the dielectric layer. In a first group of embodiments,the bottom conductive layer is prevented from abutting the dielectric inthe peripheral region by an extra layer of dielectric in the peripheralregion. In a second group of embodiments, the bottom conductive layer isprevented from abutting the dielectric in the peripheral region bycutting off the bottom conductive layer short of the peripheral region.

The present disclosure also provides an integrated circuit device thatincludes a metal-insulator-metal structure formed over the substrate.The metal-insulator-metal structure is either a resistive random accessmemory (RRAM) cell or an MIM capacitor. The metal-insulator-metalstructure includes a bottom electrode, a first dielectric layer, and atop electrode. There is a minimum distance between the bottom electrodeand the top electrode. The first dielectric layer is positioned betweenthe bottom electrode and the top electrode where they are separated bythe minimum distance. The bottom electrode and the top electrode areconfigured whereby the shortest path starting from a point on theperimeter of the top electrode and continuing to the bottom electrode isgreater than the minimum distance. In a first group of embodiments, thedistance between the electrodes is increased in the peripheral region byan extra layer of dielectric in the peripheral region. In a second groupof embodiments, the distance between the electrodes is made greater inthe peripheral region by the bottom electrode being cut off short of theperipheral region.

The present disclosure provides a method of manufacturing an integratedcircuit device that includes forming a contact on a substrate andforming one or more bottom electrode layers directly over the contact. Afirst dielectric layer is formed over the one or more bottom electrodelayers. The first dielectric layer includes a central dielectric regionin direct contact with the bottom electrode layers, an outer dielectricregion spaced apart from the bottom electrode layers, and a peripheraldielectric region that is also spaced apart from the bottom electrodelayers. The peripheral dielectric region connects the central and outerdielectric regions. One or more top electrode layers is then conformallyformed over the first dielectric layer. The one or more top electrodelayers include a central top electrode region, an outer top electroderegion, and a peripheral top electrode region. These are formed over thecentral dielectric region, the outer dielectric region, and theperipheral dielectric region, respectively. The one or more topelectrode layers and the first dielectric layer are then patterned toform a cell having a patterned top electrode and a patterned firstdielectric. The patterning removes the outer top electrode region andthe outer dielectric region while leaving the central and peripheral topelectrode regions and the central and peripheral dielectric regions.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit device, comprising: ametal-insulator-metal structure including a first dielectric layerbetween a top conductive layer and a bottom conductive layer, wherein anoutermost sidewall of the top conductive layer is aligned with anoutermost sidewall of the bottom conductive layer; a capping layerseparating the first dielectric layer from the top conductive layer, thecapping layer having a composition that differs from the top conductivelayer; a diffusion barrier layer under and contacting a bottom surfaceof the bottom conductive layer, wherein the diffusion barrier layer andthe bottom conductive layer collectively have a T-shaped profile;wherein the first dielectric layer comprises: a peripheral regionadjacent an edge of the first dielectric layer where the firstdielectric layer has been cut off by etching; and a central regionsurrounded by the peripheral region; the top conductive layer abuts andis above the capping layer; the bottom conductive layer abuts and isbelow the central region of the first dielectric layer; and the bottomconductive layer does not abut the peripheral region of the firstdielectric layer.
 2. The integrated circuit device of claim 1, whereinthe first dielectric layer and the top conductive layer are coextensive.3. The integrated circuit device of claim 1, wherein an additionaldielectric layer lies between the bottom conductive layer and the firstdielectric layer in the peripheral region.
 4. The integrated circuitdevice of claim 1, wherein the first dielectric layer is no thinner inthe central region than in the peripheral region.
 5. The integratedcircuit device of claim 1, wherein the edge of the first dielectriclayer is aligned with the outermost sidewalls of the top and bottomconductive layers.
 6. The integrated circuit device of claim 1, whereinthe diffusion barrier layer has a T-shaped profile independent of thebottom conductive layer.
 7. The integrated circuit device of claim 1,further comprising: an etch stop layer having an upward protrusionculminating in a top surface of the etch stop layer that contacts thebottom surface of the bottom conductive layer, wherein the diffusionbarrier layer extends through the etch stop layer to a bottom surface ofthe diffusion barrier layer that is even with a bottom surface of theetch stop layer.
 8. The integrated circuit device of claim 7, wherein anouter sidewall of the etch stop layer is aligned with the outermostsidewall of the bottom conductive layer and extends between the topsurface of the etch stop layer and a recessed surface of the etch stoplayer, and wherein the integrated circuit device further comprises: aconductive contact having a top surface under and contacting the bottomsurfaces respectively of the diffusion barrier layer and the etch stoplayer.
 9. An integrated circuit device, comprising: a substrate; ametal-insulator-metal (MIM) structure formed over the substrate, the MIMstructure being either a resistive random access memory (RRAM) cell oran MIM capacitor; wherein the MIM structure includes a bottom electrode,a first dielectric layer, and a top electrode, wherein the bottomelectrode has an outer sidewall which is aligned with an outer sidewallof the top electrode, wherein the top electrode includes a conductivecapping layer over the first dielectric layer and a conductive mainelectrode layer conformally overlying the conductive capping layer, andwherein outer sidewalls respectively of the conductive capping layer andthe conductive main electrode layer are aligned with the outer sidewallof the bottom electrode; the bottom electrode and the top electrode arespaced apart from one another by different vertical distances fordifferent locations across the bottom electrode; the first dielectriclayer is positioned between the bottom electrode and the top electrodewhere the top and bottom electrodes are separated by a minimum verticaldistance; and the bottom electrode and the top electrode are configuredwhereby a shortest path starting from any point on a perimeter of thetop electrode and continuing to the bottom electrode is greater than theminimum vertical distance.
 10. The integrated circuit device of claim 9,wherein the shortest path starting from a point on the perimeter of thetop electrode and continuing to the bottom electrode passes through asecond layer of dielectric that is not present on the shortest path fromthe top electrode to the bottom electrode.
 11. The integrated circuitdevice of claim 9, wherein the bottom electrode has a first widthbetween outer sidewalls of the bottom electrode, and the top electrodehas a second width between outer sidewalls of the top electrode, thefirst width and second width being equal.
 12. The integrated circuitdevice of claim 9, further comprising: an etch stop layer contacting abottom surface of the bottom electrode, wherein the etch stop layerincludes an opening under a central region of the bottom electrode; anda conductive diffusion barrier layer disposed in the opening andelectrically coupling the central region of the bottom electrode to anunderlying contact, wherein the conductive diffusion barrier layer is adifferent material than the bottom electrode and the underlying contact.13. The integrated circuit device of claim 9, wherein the conductivemain electrode layer is in direct contact with an upper surface of theconductive capping layer, and wherein the conductive main electrodelayer has a different composition than the conductive capping layer. 14.The integrated circuit device of claim 13, wherein the conductive mainelectrode layer includes a metal component, and wherein the conductivecapping layer includes a metal oxide which includes the metal component.15. A metal-insulator-metal device, comprising: a bottom metal electrodeincluding a central bottom electrode region which is laterallysurrounded by a peripheral bottom electrode region; a top metalelectrode including a conductive capping layer and a conductive mainelectrode layer conformally overlying the conductive capping layer, thetop metal electrode having a central top electrode region which isarranged over the central bottom electrode region and which is laterallysurrounded by a peripheral top electrode region arranged over theperipheral bottom electrode region, wherein a sidewall of the peripheraltop electrode region is aligned with a sidewall of the peripheral bottomelectrode region, wherein a first vertical distance separates thecentral bottom electrode region from the central top electrode regionand a second vertical distance separates the peripheral bottom electroderegion from the peripheral top electrode region, the second verticaldistance being greater than the first vertical distance; an etch stoplayer under the bottom metal electrode, wherein the bottom metalelectrode overhangs and contacts a top surface of the etch stop layer,and protrudes through the etch stop layer to a bottom surface of thebottom metal electrode that is even with a bottom surface of the etchstop layer; a first dielectric layer covering an upper surface of theperipheral bottom electrode region without extending over the centralbottom electrode region; and a second dielectric layer extending overthe first dielectric layer and extending over the central bottomelectrode region to separate the bottom metal electrode from the topmetal electrode.
 16. The metal-insulator-metal device of claim 15,wherein an upper surface of the bottom metal electrode is continuouslyplanar over the peripheral bottom electrode region and central bottomelectrode region.
 17. The metal-insulator-metal device of claim 15,wherein a lower surface of the central top electrode region is steppedrelative to a lower surface of the peripheral top electrode region, suchthat the lower surface of the central top electrode region meets thelower surface of the peripheral top electrode region at a sidewall. 18.The metal-insulator-metal device of claim 15, wherein the bottom metalelectrode has a different cross-sectional shape than the top metalelectrode.
 19. The metal-insulator-metal device of claim 15, wherein theconductive capping layer abuts the second dielectric layer and hascontours that follow those of the second dielectric layer; and theconductive main electrode layer is arranged over the capping layer, theconductive main electrode layer having a different composition than thecapping layer and having a thickness that is greater than that of thecapping layer.
 20. The metal-insulator-metal device of claim 15, whereinthe conductive main electrode layer contacts the conductive cappinglayer and comprises a recess, and wherein the metal-insulator-metaldevice comprises: a conductive via over the conductive main electrodelayer, wherein the conductive via completely fills the recess; and aconductive contact under and contacting the bottom surface of the bottommetal electrode and the bottom surface of the etch stop layer.